Drug markets may act as a causal pathway through which features of the built environment affect STI ncluding HIV vulnerability for youth. We hypothesize that features of the built environment have ndependent effects on the presence and extent of drug markets and that these markets play an important role in affecting local sexual networks and increase risks for HIV and other STIs. The proposed Career Development Award will provide Dr. Jennings with the opportunity to develop into an independent scientist who has knowledge, skills and experience to expand this avenue of research. The proposed training activities will permit Dr. Jennings to conduct independent, interdisciplinary research that melds her current discipline, epidemiology, with urban planning, drug abuse research and behavioral and developmental theory. Objectives of the training are to expand her knowledge and skills in: 1) the multi- level relationship between STIs including HIV, drug markets and the built environment; 2) social and urban policy; 3) psychological and social development of adolescents and young adults; 4) analysis of measures of the built environment and drug activities; and 5) advanced statistics including multilevel and structural equa- tion modeling. Training activities will include didactic courses, directed readings with mentors, instruction in the responsible conduct of research. Training will be guided by four prominent scholars and practitioners: Dr. Jonathan Ellen (primary mentor), Dr. Ralph Taylor, Dr. David Vlahov and Dr. Sandra Newman. The specific aims of the proposed research are: 1) to evaluate the psychometric properties of measures of the built environment and drug market activity; 2) to determine whether the built environment is significant- ly associated with neighborhood-level STIs; 3) to determine whether drug markets are associated separately with the built environment and neighborhood-level STIs; and 4) to determine in multilevel analysis, using the results of Specific Aims 1 and 2, the extent to which drug markets are in the casual pathway between the built environment and individual-level and network-level risks for STIs. Two potential confounders in our causal chain are the social environment and individual drug and/or alcohol use. The data sources will include a household study RO1 (NIAAH, PI: Ellen), on-site systematic observations and other secondary administrative data sets such as census data, police data, public health surveillance data and public housing data. The research builds on and extends the NIAAH study by moving beyond the social environment to consider the independent effect of the built environment and to consider drug markets as a mechanism of action though which the built environment may increase individual STI/HIV risk. The research is designed to culminate in the submission of an RO1 to determine the generalizability and longitudinality of the findings which will ultimately lead to a new generation of structural-level STI/HIV prevention programs among youth.